During the operation of electronically commutated motors (ECMs), asymmetries that influence efficiency can occur in the context of commutation. The reasons therefor can be categorized as either static influences or dynamic influences.
Examples of static influences are Hall sensors (or other rotor-position sensors) that are inaccurately placed, permanent magnets of the rotor that are asymmetrically magnetized or installed, leakage fluxes in the stator, and asymmetries in the motor current.
Examples of dynamic influences are rotation speed fluctuations caused by external influences, in particular changes in temperature; rotor vibrations; and software jitters. The latter are understood to be small time differences in the execution of instructions, which differences are only a few microseconds in magnitude and occur randomly, i.e. cannot be influenced.